Die head

ABSTRACT

A die head for cutting threads on a workpiece incorporating means permitting replacement of the cutting tools without disassembly of the die head and without removal of the head from the machine tool upon which it is mounted for operation.

United States Patent 1191 1111 3,731,329

Youtz et a1. 1 May 8, 1973 54] DIE HEAD 2,779,361 1/1957 MCKiff ..408713x [75] Inventors: Donald E. Youtz; Edwin M. Eigen- :22: brode, bothof Waynesboro, Pa.

1,695,158 12/1928 'Shearer ..10/100 [73] Assignee: Teledyne, Inc., LosAngeles, Calif.

FOREIGN PATENTS OR APPLICATIONS 221 Filed: Dec. 11, 1970 183,888 5/1907Germany ,.10 121 [21] App1.N0.: 97,065 1,411 5/1865 Great Britain..10/123 52 us. c1. ..10/121, 408/149, 408/178 r m 7 Lanham 511 1111.0...B23g 1/28, 823g 5/10 148mm Cmbs [58] Field 61 Search ..10 111, 120,1205 R, Attorney-Straw, N018", Neale, N168 &

10/121, 96, 100, 113, 123; 408/148, 149, 153, 173, 178, 146, 215, 231,239, 206, 713, 1 1 ABSTRACT A die head for cutting threads on aworkpiece incorporating means permitting replacement of the cutting [56]References Cited tools without disassembly of the die head and withoutUNITED STATES PATENTS removal of the head from the machine tool uponwhich it is mounted for operation. 1,045,597 11/1912 Oatman ..lO/96 R1,939,490 12/1933 Dixon ..408/146 1 Claim, 4 Drawing Figures 1- r 1 r 16o 64 1 X, 7; llY/l PATENTEDMAY' 8191s SHEET 1 [IF 3 INVENTORS DONALD E-YOUTZ EDWIN M- EIGENBRODE PATENTEDHAY 8 ms SHEET 3 BF 3 INVENTORS DONALDE- YOUTZ EDWIN M. EGENBRODE ATTORN DIE HEAD BACKGROUND OF THE INVENTIONThe present invention relates generally to self opening dies of thepull-off type. Usually die heads of thie type are components ofautomatic screw machines or turret lathes. Such die heads comprise arear part adapted for rigid connection to the associated machine tooland a forward part carrying the thread cutting chasers, the two partsbeing arranged for a limited relative axial movement. In the operationof a die head of this type, the die spindle carrying the die head isadvanced axially of the work with the chasers locked in closed positionuntil the desired length of thread has been cut. The advance of the diespindle is then halted while the forward portion of the die headcontinues to advance since the chasers will screw themselves further onto the work. The resulting separation of the front and rear parts of thedie head releases a locking mechanism to permit the chasers to withdrawradially from the work to permit removal of the finished workpiece andthe insertion of a new workpiece to be threaded.

Usually four chasers and chaser holder assemblies are employed in thistype of head. While the die head itself, as well as the chaser holders,are of extremely rugged construction and require replacement or repaironly at infrequent intervals, the chasers themselves inherently have alimited service life and require replacement at relatively frequentintervals. Similarly, replacement of the chasers and chaser holders maybe required when the workpiece size is changed.

In prior die heads of this type it has been necessary to i remove theentire die head from the machine, then disassemble the head to permitremoval and replacement of the chasers. Since the die heads are usuallya com. ponent of a larger machine the removal of a die h'ead may requirethe interruption of an entire production line.

SUMMARY OF THE INVENTION It is a principal purpose and object of thepresent invention to provide improved thread-cutting die heads in whichreplacement of the chaser holders may be effected without removal of thedie head from the apparatus with which it is associated and withoutrequiring special tools or techniques.

It is also an object of the present invention to provide improved dieheads which incorporate a mechanism to facilitate quick change of thechaser holders without adversely affecting the performance of the diehead and without significant increase in its cost or complexity.

In die heads of this type the chaser holders have integral trunnionscarried by the die head body. To move the chaser holders between dieopen and die closed positions the chaser holders are simultaneously andequally rocked about their trunnions to move the cutting edges of thechasers radially toward and away from the axis of the die head.

In accordance with the present invention, a locking member has a portionaccessible from the exterior of the die head to permit manipulation ofthe locking member between its two positions without disassembly of anyof the die head parts.

Additional objects and advantages will become apparent as the.description proceeds.

THE DRAWINGS FIG. 1 is a front view of a die head embodying the presentinvention with parts broken away to show interior details;

FIG. 2 is a section taken along line 22 of FIG. 1;

FIG. 3 is a fragmentary section taken along line 33 of FIG. 1; and

FIG. 4 is a transverse sectiontaken along line 4-4 of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now more particularly tothe drawings, the die head is provided with a tubular shank 20 adaptedto be rigidly secured to a non-rotating tool holding mechanism of amachine tool and supports the entire die head. A head body 22 is mountedon shank 20 for limited axial movement relative to the shank by means ofa tubular extension 24 which maintains the parts in coaxial alignment.The head body and the shank are held against relative rotation bydriving pins 26 pressfitted into the head body and extending with aclose sliding fit into bores 28 in the shank 20. Encircling the headbody are a closing ring 30 and an adjusting ring 32 which are held inface-to-face contact with the closing ring against flange 33 on the headbody by a spacer plate 34 which may be shimmed as required. Also mountedfor limited rotation on the head body against a rear surface of theadjusting ring is a retainer plate 35 having a rearwardly extendingexternal flange 36 surrounding a portion of the periphery of anoperating ring 38 encircling the enlarged body portion of the shankmember 20.

The retainer plate 35 is held in axial position by washers 37 held inplace on pins 26 by snap rings 39, the washers being received inrecesses 41 on the plate 35. As is apparent from the descriptionhereinabove and from FIGS. 2 and 3, the abutment surface 35a of plate 35is spaced a predetermined distance from the locating surface 23 of body22.

The chaser holders 40 are provided with trunnions 42 rotatably receivedin bores in the head body 22. The trunnions are releasably held againstaxial movement by the retainer plate 35 as described below. As inconventional prior die heads of the type with which the invention isconcerned, the rearward surfaces of the chaser holders slidably engagethe locating surface 23 of body 22, and this is clearly shown in FIG. 2.

Slide blocks 44 pivotally carried by pins 46 pressfitted into theclosing ring 30 are received in slots on the rearward surfaces of thechaser holders 40. The slide blocks are each frictionally held in properaxial position by an O-ring 45. The chaser holders are rotated betweenopen and closed positions by limited rotation of the closing ring 30.The closing ring 30 is normally held in closed position by a pair oflocking pins 50 press-fitted into the operating ring and slidablyextending through the adjusting ring into bushings 52 provided in blindbores in the closing ring. The final position of the chasers may beadjusted by operation of a worm 54 carried by the adjusting ring andpartially engaged with the head body. Adjustment of the worm rotates theadjusting ring carrying with it the closing ring.

In operation, assuming that the die is closed, and that the chasers arein engagement with a workpiece and that the die head and the workpieceare being relatively rotated and axially shifted, the workpiecethreading operation will progress until the desired length of thread isformed on the workpiece. At that time the workpiece will continue torotate, but axial advancement of the head shank 20 will be stopped. Theretainer plate 35, the head body 22, the closing ring 30 and theadjusting ring 32 will continue to move to the left. This movement willcontinue until the locking pins 50 are free of the bushings 52. As soonas this occurs, the closing ring will be partially rotated by a spring55 received in an arcuate recess 56 in the adjusting ring and actingagainst a pin 58 projecting rearwardly from the closing ring. As the dieparts are separated, springs 60 compressed between an annular face 62 onthe operating ring 38 and the head of a screw 64 threaded into theadjusting ring will be further compressed. Usually two spring assemblies60 are provided, one being shown in FIG. 2.

Also compressed during the separating action of the die parts is aspring 66 extending between a washer 68 bearing against the retainerplate 35 and the head of a pin 70 received in a recess of the head bodyand pinned to the shank as at 72. Again, to assure balanced action thedie head usually includes two of the pin and spring assemblies, one ofwhich is shown in FIG. 3.

As'soon as the chasers are disengaged from the workpiece, the springs 66urge the assembly comprising the retainer plate 35, the adjusting ring32, the closing ring '30 and the head body 22 to their original axialpositions. Since the ends of pins 50 are out of registry with thebushings 52 and engage the end face of the closing ring 30 the operatingring will be displaced to the right slightly from the position shown inFIG. 2. The die head may then be closed by automatic or manual rotationof the closing ring 30 to bring the bushings 52 into registry with theends of the pins 50. An external handle 73 may be provided on theclosing ring for this purpose. The springs 60 will then be released todisplace the operating ring 38 to the left and the parts will againoccupy the position shown in FIG. 2.

The mechanism for releasably retaining the chaserchaser holderassemblies, which forms an important aspect of the present invention,will now be described with particular reference to FIGS. 2 and 4. Asshown in FIG. 2, the trunnions 42 are provided with reduced neckportions 74 which extend through openings 76 in the retainer plate 35. Anut 78 on the trunnion extension 74 engages the rear surface 350 of theretainer plate, the adjustment of the nut determining the trunnionclearance, since the abutment surface 350 is spaced a predetermineddistance from the locating surface 23. A lock screw 80 holds the nut 78in adjusted position.

As shown in FIG. 4, the openings 76 in the retainer plate arecircumferentially elongated and include a radially narrow portion 82having a radial width slightly greater than that of the trunnion neckportion but substantially less than the width of the base of the nut 78.The openings 76 also have an enlarged essentially circular portion 84,the diameter of which is slightly greater than that of the base of nut78. Accordingly, when the retainer plate is rotated to bring the openingportion 82 adjacent the trunnion neck 74, the trunnions and theassociated chaser-chaser holder assemblies will be held against axialmovement. When the retainer plate is rotated to dispose the center ofenlarged portion 84 in alignment with the axis of the trunnions, theentire chaser-chaser holder assembly may be freely withdrawn. The slideblocks are retained on the pin 46 by the O-rings 45. Inasmuch as thefour openings 76 each occupy an identical relationship with theassociated trunnion all four chaser-chaser holders are simultaneouslylocked in place or are released, depending upon the rotated position ofthe retainer plate. To facilitate rotation of the retainer plate theexternal flange 36 is provided with a knurled surface. If desired,suitable detents may be provided to hold the retainer plate in lockingposition or to enable the operator to determine when the releaseposition has been reached.

It will be noted that the retainer plate is provided withcircumferentially elongated openings 86 to permit rotation of the platewithout interference with the locking pins 50 and the screws 64.Similarly, the elongation of the openings 76 permits the desiredrotation of the retainer plate without interference with the drivingpins 26.

In practice, when it is desired for any reason to change thechaser-chaser holder assemblies, a spare set of chasers will be properlyassembled, the chasers will be properly positioned within the holdersand the nuts 78 will be locked on the trunnions in the desired position.When the retainer plate is rotated from one limit position to another,the chaser-chaser holder assemblies will be withdrawn, the new chaserholders will be inserted into the mechanism, and the retainer platereturned to its initial position. The trunnion clearance will beautomatically correct. The chasers will also similarly be in the correctposition to permit immediate resumption of the operation of the head.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

The embodiment of the invention in which an exclusive property orprivilege is claimed is defined as follows:

l. A thread cutting die head comprising a head body assembly having alocating surface on its front face, a plurality of chaser holders havingtrunnions extending into journals in said head body assembly in adirection essentially parallel to the axis of said head, said trunnionsmounting said holders for rocking movement about the axis of saidtrunnions, said chaser holders having surfaces adapted to slidablyengage said locating surface, means carried by said bodyfor-simultaneously rocking each of said holders about the axes of saidtrunnions to move said chaser holders radially between tact with saidlocating surface on said head while permitting rotation of saidtrunnions and operative in a second rotated position to release saidtrunnions for axial movement without changing the radial position ofsaid chaser holders,said retaining plate having a portion accessiblefrom the exterior of said die head to permit manipulation of theretaining plate between said first and second positions withoutdisassembly of the die head.

1. A thread cutting die head comprising a head body assembly having alocating surface on its front face, a plurality of chaser holders havingtrunnions extending into journals in said head body assembly in adirection essentially parallel to the axis of said head, said trunnionsmounting said holders for rocking movement about the axis of saidtrunnions, said chaser holders having surfaces adapted to slidablyengage said locating surface, means carried by said body forsimultaneously rocking each of said holders about the axes of saidtrunnions to move said chaser holders radially between open and closedpositions, a retaining plate mounted for rotation on said head bodyassembly in a plane normal to the axis of said trunnions and adjacentthe inner ends of said trunnions, said retaining plate having anabutment surface a predetermined distance from said locating surface,and cooperating means on said trunnions and said plate includingadjustable means on said trunnions engageable with said abutment surfaceoperative in a first rotated position of said retaining plate to holdsaid trunnions against axial displacement with said surfaces of saidholders in light frictional contact with said locating surface on saidhead while permitting rotation of said trunnions and operative in asecond rotated position to release said trunnions for axial movementwithout changing the radial position of said chaser holders,saidretaining plate having a portion accessible from the exterior of saiddie head to permit manipulation of the retaining plate between saidfirst and second positions without disassembly of the die head.